But campaigners said this was inadequate because criteria for a conviction down these channels - such as the incident being witnessed by other people - is not always available.

Why could campaigner Gina Martin not prosecute in 2017 when she was upskirted at a festival?

Before it was made a criminal offence, the men who upskirted Ms Martin could have potentially been prosecuted for outraging public decency.

The problem was that this was not appropriate. There are two primary reasons for this.

First, the offence of outraging public decency does not apply in all instances of upskirting. This means that women are not protected in all circumstances.

Second, the offence of outraging public decency is inappropriate as it fails to reflect the sexual nature of the offence and/or the fact that the harm is caused to the individual (rather than the public).

What does the new law say?

The Voyeurism Act allows upskirting to be treated as a sexual offence and ensure that the most serious offenders are placed on the sex offenders' register.

It will capture instances where the purpose is to obtain sexual gratification or cause humiliation, distress or alarm.

What sort of sentence could a convicted upskirter receive?

A conviction at magistrates' court would carry a sentence of up to one year in prison and/or a fine.

A more serious offence, tried in the crown court, would carry a sentence of up to two years in prison.

Police will be able to arrest people on suspicion of upskirting from Friday.

What about pictures or images taken before the law came into force?

The law cannot be applied retrospectively - which means images taken before Friday cannot be considered specific upskirting offences.

That said, older images could still fall foul of other laws, such as outraging public decency.

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